Snowplows are commonly used to plow snow from roadways, parking lots and other areas. The snowplow generally consists of a plow blade, including a moldboard and a blade edge, a plow frame commonly known as a reversing table, and a support frame also referred to as an A-frame, which may be detachably mounted on the front of a motor vehicle. The snowplow blade system may be removed during snow-free months to allow other uses for the vehicle.
The snowplow blade commonly includes a blade edge mounted on a moldboard which is attached to a curved steel device, known as a reversing table. The reversing table is adapted to rotate in either direction along a supporting frame, which is generally in the shape of an A-frame. The frame is connected to the front of the motor vehicle. An upper lift arm, lifted by a hydraulic cylinder, is also attached to the front of the motor vehicle. A lifting chain, cable or lifting bar is typically attached to both sides of the reversing table and over a support mechanism in the form of a pully, link, hook, chainblock or clevis depending from the lift arm. Thus, when the upper lift arm is pivoted upwards the A-frame, the reversing table and moldboard are all raised upward and clear of the ground for transport of the motor vehicle and plow. By rotating the reversing table, either by hand or by means of hydraulic cylinders or a hydraulic motor mounted on the A-frame, it is possible to plow snow directly ahead of the plow in the manner of a bulldozer, or off to the left or right.
Prior art snowplows of this type have the drawback that when the plow assembly is lifted with the moldboard in a left or right of center position, the plow blade tilts at an angle toward the ground. The angle may be different depending on the type of blade, the nature of the mounting device and the type of vehicle to which the snowplow blade is attached. The result of this tilting is that the plow must be raised higher off the ground to clear all portions of the plow blade. This high, raised position makes the vehicle unstable and causes substantial strain on the mounting device. Additionally, there are conditions, generally deep snow, when plowing tactics require raising the blade a distance off the ground to "top" the snow. This form of "off ground" plowing is extremely difficult if the plow blade cannot be kept level to the ground. Furthermore, when the plow blade is raised to such a height to clear the ground, it tends to obscure the view of the driver of the motor vehicle. An additional problem occurs when the tilted moldboard and blade is lowered onto the ground, causing uneven wear on the corner which strikes the ground first.